BX fan

Mothman · Post by **Mothman** » Fri Apr 03, 2009 11:26 pm

Hi all,

i have a 1993 Non Turbo diesel BX estate with 120 k on the clock. Runs well, goes to Cornwall from Sussex at least once a year, oil changed regularly and does no more than about 5k a year in mileage. However, i never seem to hear the fan kick in but a friend with a heavy right foot borrowed her last year and told me she overheated on the A21[ i have never been able to make her do this] and she still runs fine.
Is this normal? should i ever hear the fan? Is there anything i can do to ensure the fan is working?
Sorry to have to ask silly questions again but ime not a BX expert but i can assure you that i am an avid BX fan and think i have an ULTRA CLASSIC car to compete with my '49 Moggie.
The BX drives[touch wood] very well, just had a new clutch and never misses a beat. I have owned her for the last 3 years, never heard the fan in all that time. Is everything ok? Should i be worried?

Andy

ken newbold · Post by **ken newbold** » Fri Apr 03, 2009 11:41 pm

You could take the car for a drive to get the engine nicely warmed up with the heater blower fan turned off.
Then lift the bonnet and let the engine idle, after a while the fan should cut it. It's not always possbile to hear it running from inside the car.

Another check worth looking at would be, check that the radiator gets hot over all it's surface, you'll need to do this with the engine hot obviously and take care not to burn yourself on the hot engine/rad. If there are any cold spots, take the rad off and give it a good flush out or replace it.
A blocked rad WILL cause head gasket failure!

DLM · Post by **DLM** » Sat Apr 04, 2009 7:34 am

Apologies for labouring a couple of points you may already have been through, but it never hurts to clean (wire-brush) the fan switch contacts (bottom l/h inner corner of the rad), and to bridge the contacts to make sure that the fan still responds to the switch. I normally gently lever the connector about 1/4" off the switch with a suitably-thin flat-blade screwdriver, then use the screwdriver blade to do the bridging.

Better still, for even more confidence in fan operation you could replace the switch itself too after checking basic for fan operation - the switches aren't wildly expensive and will degrade with age like most thermoswitches. You'll also be able to find out if the face of the thermoswitch has an insulating layer of gunge over it - often the case.

If you have a new switch to hand, you can possibly pop the new one quickly enough to avoid a coolant change if

(a)You're not familiar with the very important bleed procedure for coolant change on an XUD engine, and/or
(b) the coolant has been in place less than two years.

Without the temperature gauge that Citroen decided to forego, increasingly hot running with the passage of time isn't always apparent but not unusual, given the that the cooling system on a diesel BX is a tad marginal even when working as designed.

Mothman · Post by **Mothman** » Sat Apr 04, 2009 7:46 am

Thanks Ken and DLM for your help
Firstly i will be out and about this am and will run the checks suggested and will also look at the temp sensor.
Out of interest, where would i get a new sensor? Mail order from a Citroen specialist i suppose? My local motor factor[Lenco's in Tun Wells] probably wont have on in stock.

I havnt ever removed nor changed the coolant before, i suppose it would be a good idea to have a go, maybe over Easter would be a good time.

Andy

Post by **Tim Leech** » Sat Apr 04, 2009 10:11 am

Grenman wrote: Out of interest, where would i get a new sensor? Mail order from a Citroen specialist i suppose? My local motor factor[Lenco's in Tun Wells] probably wont have on in stock.

Andy

As they are shared with a few other citroen/peugeot cars you should be able to get one from most local motor factors (halfords etc), or www.gsfcarparts.com. As Ken and DLM says its definatly worth flushing and refilling the cooling system whilst you are at it as overheating will lead to headgasket failure!

Mothman · Post by **Mothman** » Sat Apr 04, 2009 10:45 am

Hi again,

just been on a trip with the BX and i cannot make the fan come on by letting the motor idle and have noted that the radiator is cold at the bottom. Is it difficult to flush the system and refill it?

Will have a go this pm.

Many thanks,

Andy

Post by **Tim Leech** » Sat Apr 04, 2009 11:05 am

Grenman wrote:Hi again,

just been on a trip with the BX and i cannot make the fan come on by letting the motor idle and have noted that the radiator is cold at the bottom. Is it difficult to flush the system and refill it?

Andy

Not really Andy, easiest way is to remove the radiator from the car and back flush it from the bottom and then vice versa until the water runs clear , whilst the rads out for what they cost I would change the fan switch to be safe.

The pain is bleeding the air out afterwards which may take sometime, make sure you open the bleed screws and have the heather on hot then its just a case of keep topping it up whilst ithe engines running.

Good Luck.

DLM · Post by **DLM** » Sat Apr 04, 2009 11:33 am

Last one I got came from GSF - but that was a while back, and may well have been for a turbodiesel. If going there I hope your branch is clued-up. Suggest you check the number of pins on the switch currently fitted.

On their website they currently list (can't check availability):

N93484 RADIATOR THERMO SWITCH BX ALL PETROL (SINGLE FAN MODELS) 2 PIN 10.60

N93486 RADIATOR THERMO SWITCH BX ALL MODELS WITH 2 FANS (3 PIN) 12.35

BUT from Haynes the cut-in temp specs are

Petrol models(16/19)
1st cut-in 84/6deg, 2nd 90deg
standard XUD (single fan unless 2-fan towing mod fitted )
1st cut-in 88to90deg, 2nd 90to94deg
XUD Turbo (2-fan) -
1st cut-in 93deg, 2nd 97deg

Therefore I'd quote the standard XUD spec & number of pins to whoever you speak to. The cut-ins are normally marked somewhere on the actual switch itself if in doubt.

If what GSF describe as a " 2-pin petrol switch" is compatible with your pin set-up and the same thread size, then an 84/86 cut-in for first-stage won't do any harm, particularly if radiator flow is at all restricted.

Eurocarparts list one 3-pin switch with no temp info - shown as available.

REPLACEMEN n/a 223545071 RADIATOR FAN SWITCH 3 PIN BX/CX/VIS.
Three Pin Black £13.25

Do bear in mind that the sensor is the bottom-pipe end of the coolant flow where hopefully the radiator has already done some cooling so it'll be hotter further back at the engine end.

Mothman · Post by **Mothman** » Sat Apr 04, 2009 2:18 pm

Hi again guys,

have got the rad out, that wasnt without its problems and have backwashed it but i feel for not enough time. No gunge came out although the water was not clean. Originally it was blue with the antifreeze.
Am off to Lenco's with the old sensor and will let you know how things progress. I can tell you that i havnt done anything like this before so its uncharted territory for me and the trusted Haynes manual.
Fingers crossed.

Andy

ken newbold · Post by **ken newbold** » Sat Apr 04, 2009 3:36 pm

MAKE SURE YOU BLEED THE SYSTEM CORRECTLY BEFORE TAKING THE CAR ON THE ROAD

It's easy enough to do

Mothman · Post by **Mothman** » Sat Apr 04, 2009 4:33 pm

ken newbold wrote:MAKE SURE YOU BLEED THE SYSTEM CORRECTLY BEFORE TAKING THE CAR ON THE ROAD

It's easy enough to do

Hi Ken,

all done and rad back. Spent a while topping up the rad whilst the engine was running with the bleed screw on the rad and the small white one on the pipe leading to the block and just kept slowly adding and adding.
Ran the engine for a while with the rad cap off, gently pushing down on the front and a few larger bubbles apperared then no more. Will do it again in a minute. Tightened up the bleed screws whilst they were leaking fluid. Hope this was all ok?

At least if i need a new rad, i will have no problems in replacing it myself.

Thank you all who posted on this thread. Gave me the confidence to get on with it. Its a great pleasure to know that there are such kind, helpful people about.

Thanks once again

Andy

Post by **Tim Leech** » Sat Apr 04, 2009 10:07 pm

Great news Andy, just keep checking the levels

Mothman · Post by **Mothman** » Sat Apr 04, 2009 10:16 pm

Roverman wrote:Great news Andy, just keep checking the levels

Will do bud,
however i have found that the bottom of the rad is still cold and even after driving for a couple of miles the rad is still not very warm, and the fan wont come on at idle. Have replaced the sensor. Is it looking like a new rad? Well, at least its an easy job now.I did see a yellow wire attached to nothing whilst removing the rad, it had a free end, should i be worried?
Many thanks,

Andy

ken newbold · Post by **ken newbold** » Sat Apr 04, 2009 10:52 pm

The plug which fits onto the rad temp switch has three connections. One horizontal and two vertical. If you short the horizontal one to either of the vertical ones with a piece of wire, the fan should cut in, slow or high speed whichever side you short out. (ignition on but engine not running)

This will tell you if the fans are OK. Also it can take ages for the thermostat to open when the engine is ticking over. Be certain the thermostat has opened and the rad is still cold at the bottom before investing in a new one.

Mothman · Post by **Mothman** » Sun Apr 05, 2009 9:32 pm

Hi Ken,
rad still very cold at the bottom, even after a long run, zakly as it was before so methinks a new one is needed so will have to source another. Maybe thats why the fan wont work as the rads not hotting up enough, however will test the fan as you suggestyed but after a 30 min drive it was stone cold at the bottom.
Tanks once again for your help and am glad the forums up and running again.

Andy